Coffee: Caffein and Chlorogenic Acid
We have learnt about the volatile compounds that affect the aroma of coffee in the previous article: Arabica Coffee Extraction Optimization using HS-SPME/GC-MS - Journal of Science & Applied Chemistry.
Just as important as the aroma, many coffee drinkers agree that the coffee taste plays a major role in the overall quality. Coffee is known to have a bitter taste which comes from caffeine. In addition, coffee also has a sour taste which comes from chlorogenic acid. Let’s look at these two main compounds that affected the taste of coffee in more details.
Caffeine is a white colored powder with no smell but has a bitter taste . Caffeine contributes to about 10-30% of bitter taste in brewed coffee . It also contributes for the nice aroma of coffee. From research, it was found that the roasting process causes a small amount of caffeine compound to evaporate and transform into other compounds such as acetone, furfural, ammonia, trimethylamine, and acetic acid .
Today, it is well known that coffee helps combat drowsiness. It is because when we drink coffee, the caffeine molecule would inhibit adenosine, a compound in the brain cells that responsible for making one fall asleep. Caffeine reverses the action of adenosine so that drowsiness disappears, causing a feeling of freshness, joy, eyes wide open, heart beating faster, blood pressure rising, muscles contracting, and liver releasing sugar into bloodstream so that one will feel full of energy .
When consumed in low doses, caffeince can increase stamina and relieve pain. Meanwhile, if caffeine is consumed in excess amount, it can cause insomnia, irritability, and worry .
2. Chlorogenic acid
Chlorogenic acid is the main phenol component in coffee, which is one of the antioxidants that plays an important role in food. The concentration of chlorogenic acid in coffee beans is quite high at about 4 to 14% . Some of the benefits of chlorogenic acid includes: preventing the genotoxicity of monochloramines of the gastric mucosa , inhibiting the risk of coronary heart disease, having antibacterial, antiviral, anticancer activity, and reducing the risk of coronary heart disease, reducing body weight, as well as reducing the risk of DM II .
Based on its chemical structure, chlorogenic acid is combination of esters and acids from two acids, namely caffeic acid and quinic acid. Caffeic acid is responsible for the bitter taste, while quinic acid is responsible for the sour and astringency.
Moreover, chlorogenic acid has many isomers that are found in brewed coffee, such as (a) 3-Caffeoylquinic acid (3-CQA); (b) 4- Caffeoylquinic acid (4-CQA); (c) 5-Caffeoylquinic acid (5-CQA), (d) 3- Feruloylquinic acid (3-FQA), €4-Feruloylquinic acid (3-FQA), 5- Feruloylquinic acid (4-FQA), 3,5-diCaffeoylquinic acid (3,5-diCQA), 4,5- diCaffeoylquinic acid (3,5-diCQA), 3,4-diCaffeoylquinic acid (4,5-diCQA).
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